You can use Digital Signature Certificates for the following:

For sending and receiving digitally signed and encrypted emails .For carrying out secure web-based transactions, or to identify other participants of web-based transactions.In eTendering, eProcurement, MCA for Registrar of Companies efiling, Income Tax for efiling income tax returns Applications and also in many other applications.For signing documents like MSWord, MSExcel and PDFs. Plays a pivotal role in creating a paperless office.